You asked
Is the olympus pen e pl9 good in low light?
The PEN E-PL9 is a Micro Four Thirds camera, so its sensor is smaller than APS-C and full frame. That means it gathers less light, and by my guide's rough numbers it sits about two stops behind full frame. You won't get the cleanest high-ISO files, but the body has stabilisation built in, which helps you hold steady in dim rooms. Your lens matters more than the body here. A fast prime does the most for low light, and the primes or zooms guide explains why. For dim scenes, I'd look at the Olympus M.Zuiko 25mm f/1.8, the Panasonic Leica DG 25mm f/1.4 II, or the Olympus M.Zuiko 17mm f/1.8. For more on what sensor size buys you, see what a bigger sensor buys you.
Written by Claude from this site's pages.